1. Field of the Invention
The present invention relates to systems and methods for enhancing water pump seal performance in a water/coolant pump for an internal combustion engine.
2. Background Art
Internal combustion engines typically have a liquid cooling system that uses a water pump to circulate engine coolant between a radiator and the cooling water jacket of the engine. A typical centrifugal water pump consists of a shaft mounted impeller rotatable inside a housing. The shaft is substantially part of an integrated shaft bearing which is pre-lubricated and located in an environment free of debris and coolant. A mechanical seal with sliding faces is disposed about the shaft and mounted in the housing inside a seal cavity behind the impeller to prevent leakage of coolant into the area where the bearings support the shaft and/or outside of the housing. The mechanical seal relies on a lubricating fluid film to inhibit or prevent deterioration of the sliding faces by separating the faces and providing cooling. Static pressure at the seal may facilitate exchange of thermal energy between the sealing surfaces and surrounding fluid by maintaining the fluid in the liquid phase. Vaporization at the sealing surfaces can lead to contact between the seal faces, causing early wear and adversely affecting desired seal performance. Similarly, any debris and/or contaminants in the water/coolant may collect in the seal cavity and lead to scoring of sealing surfaces resulting in fluid leakage past the seal.
U.S. Pat. Nos. 5,713,719 and 5,355,847 disclose water pump features designed to increase the coolant velocity at the seal to flush debris and cool the seal, or to increase structural integrity of the pump. However, the present inventors have recognized that increasing coolant velocity at the seal alone will not necessarily improve seal performance, and may actually adversely affect seal performance. The present inventors have recognized that prior art water pumps do not recognize the role of static pressure and coolant velocity at the seal relative to seal performance.